The present invention relates to a commutator in which predetermined commutator pieces are short-circuited, and to an armature.
In the prior art, an armature for a motor having power feeding brushes may include a commutator in which a plurality of commutator pieces are short-circuited. Such a motor allows electric current to flow even to commutator pieces that are not in contact with power feeding brushes by short-circuiting predetermined commutator pieces. This enables a reduction in the number of power feeding brushes required in the motor.
In one example, in a rotating armature described in Japanese Laid-Open Patent Publication No. 2000-134873, a plurality of short-circuit conductors for short-circuiting commutator pieces of a commutator are arranged to overlap one another at an axial end portion of the commutator.
However, when the short-circuit conductors are arranged to overlap one another at the axial end portion of the commutator, the overlapping short-circuit conductors increase the length of the commutator in the axial direction, which in turn, increases the length of the armature in the axial direction. Further, the overlapping short-circuit conductors may rub against one another. This may rub off the coating of the short-circuit conductors. In such a case, the short-circuit conductors may be electrically connected (layer short). This may lower the manufacturing yield of the armature or cause erroneous operations of the armature and may eventually lower the reliability of the armature.